Exhausted from overwork and a punishing travel sched­ule, a rail-thin ANGELINA JOLIE suffered a frightening collapse on her Australian film set!

The black-clad Oscar winner crumbled to the ground while directing the World War II-era drama “Unbroken.” Sources say terrified crew and cast members rushed to Angelina’s side, fearing she’d actually died. But the 38-year-old actress brushed off their concerns and re­sumed working.

Now friends, family members and even medi­cal experts are concerned that Angelina – who under­went a double mastectomy and breast reconstructive surgery earlier this year – could suffer severe heart problems if she doesn’t cut back on her grueling pace.

“Angelina’s been putting herself through the wringer, and it’s taken a severe physical toll on her body,” said a source. “She’s been working around the clock – directing at least nine to 12 hours a day and looking after her kids.

“She’s dropped to a skeletal 93 pounds, and being so thin can place a tremendous amount of pressure on the heart. Angelina could easily suffer a heart attack and die!”

The “Salt” star’s latest health scare unfolded on Dec. 2 while she was direct­ing several actors dressed as soldiers while they rehearsed a scene.

As she was showing them what she wanted them to do, her legs buckled, her head rocked back and she slumped to her knees, sources say.

“When Angelina dropped to the ground, some of the cast and crew weren’t sure what was going on,” said the source. “At first, they thought she was play-acting. Then, they rushed to her side, believing she was seriously ill – or worse, dead!

“She was sickly pale and gasping for air. But Angie refused to be taken to the hospital. After she composed herself, she assured everyone she was fine and went right back to work.”

“She may not be getting enough nutrients, includ­ing essential vitamins, minerals and fluids, to keep her heart healthy,” Dr. Gabe Mirkin – a board-certified physician from Or­lando, Fla., and author of “The Healthy Heart Miracle” who has not treated the actress – told The ENQUIRER.

“When the heart is deprived of these essential nutrients, it can increase one’s risk of heart attack.”

She’s crisscrossed the Pacific Ocean nu­merous times since September, when she scouted “Unbroken” locations in Hawaii and Australia, jetted to Hong Kong to meet up with fiance Brad Pitt, and then flew back to Australia to work.

In November, Angelina flew to California to attend the Governors Awards in Holly­wood with Brad, 49, and their son Maddox, 12. Afterward, she immediately headed back to the “Unbroken” set in Australia. “The constant air travel increases her risk of dehydration,” noted Dr. Mirkin.

“That can cause an imbalance of the body’s electrolytes, potentially causing life-threatening swelling of the brain and seizures In addition, she’s probably not getting enough sleep, which research shows can cause a multi­tude of health problems.”

Dr. Craig Title, a weight-loss specialist from New York City who has not treated Jolie added: “Being significantly underweight can be very unhealthy. It can cause malnutrition leading to osteoporosis, iron deficiency anemia, loss of po­tassium which leads to impaired heart and muscle function, hormone imbalance and infertility.

“Malnutrition can also cause heart arrhythmia due to muscle wasting which can be life-threatening.”

Experts say that an average woman of An­gelina’s 5-foot-7 height should weigh between 130 and 140 pounds. But maintaining a healthy weight has been a constant struggle for the “Mr. & Mrs. Smith” star.

In 2009, we reported the mother of six had dropped to 104 pounds. And as we recently re­vealed, an emaciated Angelina feared she had as few as three years to live and secretly compiled a “bucket list” of goals to complete before she died.

Her on-set collapse happened shortly after Brad flew back to England following a visit to Australia, where he’d spent Thanksgiving and Pax’s 10th birthday on Nov. 29. Sources say Angelina was beginning to show signs of exhaustion while the whole family was together but refused to let it ruin the fun, said the source. She joined Brad and the kids for an outing aboard a luxury yacht in Sydney Harbor as well as a “Roar & Snore” adventure at the Taronga Zoo that included visits to the animal attractions followed by a sleepover.

“Angelina put on a brave face, even though she was dead tired,” said the source.

“She especially didn’t want to share her physical problems with Brad because she knew he’d be worried sick.”

When Angie collapsed, the source says Brad panicked and wanted to fly straight back to Australia, but she convinced him to fulfill his obligations on his set before joining her. Added the source: “Brad now plans to rush back to Australia as soon as his film ‘Fury’ wraps in England.”